Spinon heat transport and spin-phonon interaction in the antiferromagnetic spin-1/2 Heisenberg chain cuprates Sr2CuO3 and SrCuO2

TL;DR

This study investigates heat transport via spinons in Sr2CuO3, revealing how spin-phonon interactions influence thermal conductivity and demonstrating the effects of impurities and temperature on spinon mean free paths.

Contribution

It provides detailed measurements of spinon thermal conductivity and mean free paths in high-purity Sr2CuO3, and compares spin-phonon interactions across similar compounds, linking experimental data with theoretical models.

Findings

Spinon mean free path at low T is about 0.5 μm.

Spinon-phonon scattering dominates at higher T, following an exponential decay.

Spin-phonon interaction strength is similar in Sr2CuO3 and SrCuO2.

Abstract

We have investigated the thermal conductivity \kappa_mag of high-purity single crystals of the spin chain compound Sr2CuO3 which is considered an excellent realization of the one-dimensional spin-1/2 antiferromagnetic Heisenberg model. We find that the spinon heat conductivity \kappa_mag is strongly enhanced as compared to previous results obtained on samples with lower chemical purity. The analysis of \kappa_mag allows to compute the spinon mean free path l_mag as a function of temperature. At low-temperature we find l_mag\sim0.5\mum, corresponding to more than 1200 chain unit cells. Upon increasing the temperature, the mean free path decreases strongly and approaches an exponential decay ~1/T*exp(T*/T) which is characteristic for umklapp processes with the energy scale k_B T*. Based on Matthiesen's rule we decompose l_mag into a temperature-independent spinon-defect scattering length l0 and a temperature dependent spinon-phonon scattering length l_sp(T). By comparing l_mag(T) of Sr2CuO3 with that of SrCuO2, we show that the spin-phonon interaction, as expressed by l_sp is practically the same in both systems. The comparison of the empirically derived l_sp with model calculations for the spin-phonon interaction of the one-dimensional spin-1/2 XY model yields reasonable agreement with the experimental data.